A new therapy based on gene base editing is helping patients fight against previously incurable T-cell leukemia. The treatment involves modifying the T-cells: removing the CD7 marker to prevent their self-destruction, removing the CD52 marker to protect against antibodies, and adding the CAR receptor to attack the leukemic T-cells. The results of the first study on 11 patients from Great Ormond Street and King's College Hospital were published in the New England Journal of Medicine. The therapy achieved undetected leukemia in patients, followed by a bone marrow transplant. About 20% of children with T-cell leukemia do not respond to standard treatments such as chemotherapy or a transplant. The first patient, 13-year-old Alyssa diagnosed in May 2021, did not respond to standard therapies and was given an experimental treatment instead of palliative care; he is now under long-term follow-up with undetected leukemia. The therapy is prepared in advance as an "off-the-shelf" product for emergency cases and combines intensive immune therapy with transplantation for long-term survival. Great Ormond Street Hospital Charity will support the treatment of 10 more patients.